During 2010’s Deepwater Horizon oil spill there were reports of underwater plumes of oil escaping collection. This video demonstrates how such a plume can form. There are two clips shown here; in both the tank is filled with salt water of varying salinity, with denser saltwater at the bottom. The first jet is a green alcohol/water mixture and the second is a red gauge oil. Both jets have the same density and flow rate, but they vary in their Reynolds number. The first turbulent jet gets trapped at the interface between the denser and lighter saltwater while the less turbulent red jet passes the interface with no difficulty. The researchers suggest that strong turbulence can create an emulsion, a mixture of two normally immiscible fluids–imagine shaking a container of oil and vinegar really well–which can lead to underwater trapping.